Travel in Space: To the Moon and Beyond
The rocket engine, with its steady roar like that of a waterfall or a thunderstorm, is an impressive symbol of the new space age. Rocket engines have proved powerful enough to shoot astronauts beyond the earth's gravitational pull and land them on the moon. We have now become travelers in space.
Impressive and complex as it may appear, the rocket is a relatively simple device. Fuel that is burned in the rocket engine changes into gas. The hot and rapidly expanding gas must escape, but it can do so only through an opening that faces backward. As the gas is ejected with great force, it pushes the rocket in the opposite direction.
There are many problems connected with space travel. The first and greatest of them is gravity. If you let your pencil drop to the floor, you can see gravity in action. Everything is held down to the earth by magnetic force. The weight of something is another way of describing the amount of force exerted on it by gravity. A rocket must go at least 2500 miles an hour to take anyone beyond the gravity of the earth into space.
Another problem is the strain that a person is subjected to when a rocket leaves the ground. Anything that is not moving tends to resist movement. As the rocket leaves the ground, it pushes upward violently, and the person in the nose is pushed back against the chair. During this thrust, gravity exerts a force on the body equal to nine times its normal force.
Once out of the earth's gravity, an astronaut is affected by still another problem --- weightlessness. Here,if a pencil drops, it does not fall. If a glass of water is turned upside down, the water will not fall out. All of us who are used to gravity expect things to have weight and to fall when dropped. Our bodies, which are accustomed to gravity, tend to become upset in weightless conditions. Recent long flights have shown that the body needs special exercise in a spaceship.
Cosmic rays and tiny dust particles also raise a problem. Outer space, which has no air, is filled with both of these. The dust particles can damage the front end of the rapidly moving spaceship. The cosmic rays,though they are invisible to the naked eye, can go through the ship and the astronauts themselves. No one is sure what damage the cosmic rays can do to a human being, but scientists feel that brief exposure is probably not very harmful.